


Waterworks

by plaidagladalecki



Category: Supernatural
Genre: Destiel - Freeform, Fluff, M/M, Mermaids, merman!Castiel, siren!Dean
Language: English
Status: Completed
Published: 2016-06-30
Updated: 2016-07-09
Packaged: 2018-07-19 04:03:10
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 3
Words: 2,844
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/7344007
Author URL: https://archiveofourown.org/users/plaidagladalecki/pseuds/plaidagladalecki
Summary: <blockquote class="userstuff">
              <p>Dean is a siren and Castiel is a merman and they live together and are super cute.</p>
            </blockquote>





	1. Chapter 1

Oh, take your time, don’t live too fast  
Troubles will come and they will pass  
You’ll find a merman and you’ll find love  
And don’t forget, son, there is someone up above

“Simple Man” was one of Dean’s favorite songs, and particularly one of his favorite songs to sing when he was taking a shower. His voice was enchanting and mesmerizing, and Cas, whether he liked it or not, was controlled by it and followed it to the bathroom, where Dean then proceeded to splash water on him. Cas was never enthused by this because every time Dean splashed him, he ended up sprawled out on the bathroom floor, blue fish tail and all. Perhaps a merman living with a prankster siren wasn’t such a good idea after all…  
Cas had expressed to Dean many times that he didn’t enjoy going fish-mode without consent, but Dean seemed to find it hilarious every time it happened. He would wander into the bathroom, get splashed, grow a tail, and Dean would leave him alone on the floor to drag himself over to the pile of towels and spend at least twenty minutes drying himself off completely so that he would regain his legs. But, nevertheless, it always happened. Dean’s voice was irresistible.  
Tonight, however, was a little different. Dean was in their backyard pool, relaxing in the deep end, wistfully singing that same song. At first, Cas hated it (he wasn’t a fan of 70’s music), but, after hearing his love sing it so often, he grew to love it, too. Naturally, Cas followed the sweet notes of Dean’s voice outside, and fell right into the shallow end of the pool. He immediately transformed, and his blue-black scaly tail was exposed, along with webbing between his fingers and gills on his neck. However, he wasn’t irritated this time; At least he was in a body of water and not laying on the floor.   
“Hey, Cas. Glad you could make it,” Dean crooned with a smirk across the pool, treading water. Cas smiled and dove in, swimming over and emerging right in front of Dean, tickling his feet with his long tail fins.   
“This is pretty different from your usual routine, don’t you think?”  
“Yeah, but that one got old. And my dumb ass finally realized how much it annoyed you. Plus, I just really needed a swim and I love the way the moonlight reflects off of your scales.” He gently caressed Cas’ face, admiring how his jet black and soaking wet hair made Cas’ skin look even paler, and how the navy of his tail brought out the sapphire of his eyes. Dean reached behind him for a small black remote and punched a button on it. Within a few seconds, the whole pool changed color. There were underwater lights that changed the water from red to blue to green to yellow and back again. They both had huge smiles on their faces, admiring the aquatic aurora.   
Cas looked at Dean mischievously. He planted his hands on Dean’s shoulders and thrusted the two of them down into the water. Cas wrapped his tail around Dean and kissed him hard on the lips. Dean hummed with delight and Cas had never felt more in love. After a minute or two, Dean started kicking about and Cas knew that he had to let him come up for air.   
“Sorry, Dean. Forgot you had to breathe,” Cas said after they erupted from the water.   
“Yeah. Breathing is such a chore. Sirens can hold their breath for a few minutes down there, but we don’t have gills,” Dean chuckled.   
Cas placed his hands on Dean’s pectorals and pushed him to the end of the pool, using his powerful tail as a motor. Cas kissed Dean again, figuring that doing this with both of their faces out of the water would be a better idea. Dean continued to chirp and moan every other kiss, and the two fins on Cas’ hips fluttered every time.   
Before long, the two of them were panting, and Dean’s legs were getting tired from treading water all that time.   
“How about I dry you off and we can continue this someplace else,” Dean said, out of breath. Cas nodded. Dean scooped him out of the water and onto the pavement, and Dean climbed out after him. He carried Cas over to one of the reclining beach chairs and set him down. He reached over to the large stack of beach towels and grabbed one, beginning to dry Cas off, still making happy sounds in the back of his throat as he went. Before long, Cas’ legs were back and his neck hadn’t slits on either side. He sat up and followed Dean into their bedroom, laying down on the bed together and placing sweet kisses onto each other's lips until Cas’ eyes started drooping and Dean serenaded him off to a dream-filled sleep.


	2. Chapter 2

**Summary for the Chapter:**

> Cas wakes up from a nightmare and cuteness ensues.

**Notes for the Chapter:**

> Shoutout to user Tullooa for inspiring me to write this next part :)

Dean woke with a start, Cas tucked under his arms, grunting and twitching in his sleep. He glanced over Cas’ body at the clock, and it read two o’clock in the morning.  
“Cas, baby, wake up,” Dean said worryingly, shaking Cas by the shoulders.  
Cas jolted awake with a startled half-yell. He looked around the room, panting, then locked eyes with Dean and relaxed a little.  
“What’s the matter, Cas, huh? Did you have a nightmare or something?”  
“Yeah, I guess I did. Don't worry about it, go back to sleep,” Cas said, starting to roll back over.  
“No. Cas, you’re sweating. You were practically seizing in your sleep. I want to know what happened up there,” Dean said, tapping Cas’ forehead with his index finger.  
Cas sighed, then reluctantly realized that Dean was not going to give up on this.  
“I was having a dream that… Well, that you were drowning. You were drowning because of me and I held you under too long and it was my fault--”  
“Hey, shh, it's okay. Come here,” Dean said as he wrapped Cas up in a hug. Cas was sobbing. He had had nightmares before, but none where his reaction to them was this strong. “I'm right here, Cassie, alright? You didn't do anything wrong. I'm okay, you’re okay…” Dean rubbed Cas’ back with one hand and ran the other hand through his hair, Cas’ face pressed into Dean’s shoulder. Dean started to coo and sing a light little song to calm Cas down, and eventually he did. Sometimes, being a siren was more of a curse than a gift, but if he really concentrated on his pitch, he could sing to calm rather than to lure.  
Cas removed his head from Dean’s shoulder and looked into his eyes, both of them holding onto each other’s faces.  
“I’m not going anywhere, right Cas?” Dean said, smiling at the merman in front of him. Dean pressed his lips to Cas’ ever so delicately, chirping in the back of his throat. This was how they both liked their relationship: sweet and innocent. People used to say to them that a relationship between their two species would never work out, but Cas and Dean were determined to prove them wrong. Dean learned how to use his voice to soothe rather than to kill, and Cas never had anything to worry about in the first place. They felt like they were meant to be together, meant to protect each other. They fit together like two puzzle pieces, and they were perfectly content to spend the rest of their lives together living on their own private oasis where the sea would always be there to greet them.  
“Think you’ll be able to go back to sleep?” Dean asked Cas.  
“Probably not. I usually go for a swim when I wake up like this.”  
“Let's do it, then,” Dean replied, smiling at Cas.  
The two of them got out of bed and walked, hand in hand, down to the shore to their usual spot. Dean sat down on one of their beach chairs and watched as Cas ran into the waves and disappeared, only to be spotted again a few yards away, translucent blue tail fins flipping and splashing in the water.  
Dean loved watching Cas just swim. Sometimes, Dean wished he could have a tail of his own and be able to spend hours underwater without ever coming up for air. But, until that happened, watching Cas be happy in his element was the greatest joy he had ever felt.  
Suddenly, a familiar figure appeared in the sand, delicate foamy waves washing over that iridescent navy blue tail.  
“Come join me, Dean. I want to show you something.” Dean smiled and complied, getting up from his cozy position and wading into the water. Cas grabbed onto his wrist, pulling him under the water and swimming alongside him to a spot where the moonlight shone down in little spotty rays. Cas and Dean looked at each other, and Cas motioned for Dean to look down. All around the ocean floor were what seemed to be hundreds of different shells. Large conches, abalone, and cowry shells were all arranged, reflecting the light beautifully. It took Dean a moment to realize that the shells formed the words “I love you”.  
Dean was blushing and he tried to turn away from Cas. His smile was so big that his cheeks began to hurt. Just then, Cas placed his hand on Dean’s cheek and turned his face towards his own, placing a sweet kiss on Dean’s lips. Cas wrapped his tail around Dean’s legs so that they would stay put together, and he embraced Dean with both arms. They continued to kiss each other, tasting each other’s lips, bubbles emitting from Dean’s parted mouth every time he would let loose an occasional note.  
After a few minutes, Cas realized that Dean needed to breathe, so he let go and they both swam upwards until their heads breached the water.  
“I love you too,” Dean said, treading water and looking into Cas’ eyes. They both smiled at each other and they both knew that their love was sincere. “Think you’ll be good to get back to sleep now, baby?”  
“Only if you sing me to sleep again,” Cas said mischievously. The two of them swam back to shore, Dean picking up Cas and cradling him once they reached the sandy beach and carrying him back to bed. The late night beach breeze dried off Cas as they went so that he was perfectly human again by the time they reached the bedroom.  
Dean placed Cas down on the silky comforter and crawled into bed after him, Dean playing the role of “big spoon” as per usual.  
“What’ll it be this time, huh? What song would you like?” Dean whispered to Cas, gently kissing his jawline and brushing his calloused fingers through Cas’ dark ebony hair.  
“I like it when you improvise,” Cas said, already sounding sleepy.  
“Alright, baby. Original Dean Winchester it is.” Dean paused and thought for a moment before humming a soft, nautical-sounding melody. His voice sounded mostly human, but with a sound something like whale song behind it. It resonated all around the room, the sweet notes piercing through any of Cas’ memories of his nightmare and coaxing him into a deep sleep, knowing that his Dean was right beside him, not going anywhere.


	3. Chapter 3

**Summary for the Chapter:**

> The classic story of "Waterworks" featuring Sabriel.

**Notes for the Chapter:**

> Once again, shoutout to Tullooa for encouraging me to keep writing this series. :)

Dean slowly woke up and blinked hard a few times to get some moisture back in his eyes. He looked over at the clock and realized what day it was.  
“Shit! Dammit, Sam is gonna be here any minute! Get up, Cas, come on,” Dean shouted, shaking Cas awake by the shoulders. It took him a few seconds to register what Dean had just said.  
“Oh, man, you’re right!” They sprung off of the bed and threw random t-shirts and pants at each other, smelling them first before putting them on. When their clothing looked decent enough, they turned around to look at each other.  
“Come ‘ere,” Dean said, taking a step toward Cas. He licked his fingers and ran them through Cas’ hair, trying to get rid of his messy, but sexy all the same, bed-head.  
“Ew, gross, Dean. Stop that,” Cas said through giggles.  
“I know, I'm gross,” Dean replied, pecking Cas on the cheek. “Alright, why don't you go brush your teeth or somethin’ and I'll try to fix the place up a little--” the doorbell interrupted them. “Well, no time for that. You can go do whatever, I'll let Sam in and stall, ‘kay baby?” Cas nodded with a small smile and left the bedroom. Dean smoothed his own hair a little and slapped himself lightly in the face to wake up a little more, then proceeded to the front door.  
“Hey, Sammy!” Dean said, embracing his younger brother and clapping him on the back after he opened the door. “Come in, man--oh, hey Gabe… Uh, long time no see!” Dean said, looking from Sam to the man standing next to him. “Come on in, both of you.”  
Sam and Gabe stepped into the entryway and looked around.  
“Nice place you got here, Dean-O,” Gabe said with approval. Just then, Cas stepped out of the bathroom. Sam was understandably surprised when he saw him. They took a few looks at each other, registering each other’s presence.  
“Oh, hey, Cas… Didn't expect to see you here,” said Sam with a friendly smile, sizing him up and glancing back at Dean. “Can I talk to you outside, Dean?”  
Dean followed Sam back out the door and Sam closed it behind them.  
“So, you and Cas, huh? Never expected that to happen.”  
“I can say the same about you and Gabe. I thought you guys had a thing back in the day and then cut it off ‘cause you thought you were straight.”  
“I mean, yeah, we did. But he was just in town one day and it just clicked, I don't know. He just feels right, you know?” There was a silence and Dean nodded. “So… How are you and Cas working, with the whole siren thing and all?”  
Sam knew since the first time he heard Dean cry as a child that he was a siren. Traditionally, sirens lure human sailors to their watery graves with their hypnotizing voices. Merpeople can’t technically “drown” because they have gills, but the pitch of a siren’s song is still quite irritating and sometimes painful to the eardrum. Sam always accepted and loved Dean for who he was, but their merperson parents always favored Sam and shoved Dean aside sometimes; sirens were looked down upon as “pests” or “dangerous”. But, Dean always loved Cas, and he was determined to erase the stereotype against sirens.  
“We’re fine,” Dean said, remembering their pool rendez-vous the night before. “I figured out how to sing without bursting his eardrums, so that's nice.” Sam chuckled. “How are you and Gabe working out? He’s one of you, too, right?”  
“Yeah, he is ‘one of me’. We’re doing just fine, Dean. It’s good to see you’ve made things work.” With that, the two of them reentered Dean’s home, pleased to see Gabe and Cas picking up where they left off. The two of them were members of the same clan, so they had known each other previously.  
“Hey, Dean, babe, can I talk to you?” Cas said, innocence in his eyes but a darker tone lurking in his voice. He nodded to Cas and they retreated back into their bedroom to talk.  
“Did you not tell Sam that you and I were together?” Cas asked, squinty-eyed and with arms crossed.  
“Well, no, I--”  
“Are you ashamed of me, Dean?”  
“No, of course not! Look, Cas, it’s--” Dean trailed off, pondering whether he should open up about why Sam never knew about Dean and Cas before now. Cas must have gathered from talking to Gabe and from the way Sam reacted at seeing him that neither of them were told anything. “I’m not ashamed of you, Cas. Why would I be? My own brother is a merman, for Christ’s sake. You’re beautiful, Cas, and I love you. I didn’t want Sam trying to talk me out of being with you, so I never told him. In your world, I’m a nuisance. I’m a danger. Sam was always trying to look out for me and I knew he would try to pull me away from you, but I loved you so much, so I--” Dean was suddenly cut off by two plush lips firmly planted on his own.  
“I’m sorry, Dean. I should have known.” They smiled at each other. “I think your singing is beautiful. You’re not a nuisance. Well, I mean, sometimes you are, but I don’t mind it,” Cas said, earning a giggle from Dean. “I love you too.”  
With that, the two of them strolled back into the entryway, where Sam and Gabe were still standing.  
“Anyone up for a swim? I’ll provide mood music” Dean suggested, smiling at all of them.


End file.
